A definitive evaluation of tumor markers has been hindered by a lack of adequate number of patient's specimens and :the lack of adequate follow-up or patient information, the variability in therapeutic modalities, and poor computerization systems to retrieve the desired cases for performing these studies. Therefore, what is needed is a breast cancer tissue resource that would be able to provide archival breast tissue in sufficient amount to allow researchers to draw valid statistical conclusions, based on the stage of the disease, treatment modality, follow-up, adequate histological diagnosis, lymph node status, tumor grading and other demographic data such age, menopausal status and race among others. For answering these needs we have organized the Fox Chase Cancer Tissue Resources (FCCC-BCTR). The FCCC-CBCTR has been one of the four pillars for the creation of the National Cancer Institute Cooperative Breast Tissue Resources (NCI-CBCTR). The FCCC-BCTR has contributed during the last eight years with more than 2,859 cases to the total of 9,000 cases available in the NCI-CBCTR database. The collected cases contain the archival paraffin tissue, data on demography, pathology, clinic, treatment, and their respective clinical follow-up. Recently we have been developing the tissue microarray as a more efficient way to provide large amount of cases with minimal amount of resources to the researchers. Based on this contribution we propose the following specific aims for the maintenance of the FCCC Breast Tissue Resources as part of the NCI-CBCTR: 1: To provide tissue sections and pertinent clinical data to investigators whose applications have been recommended for approval by merit and content by REP and approved by the NCI-CBCTR. This work will be done in cooperation with the other resources of the NCI-CBCTR. 2: To actively participate in the construction of tissue microarray and further distribution to investigators whose applications have been recommended for approval by REP and by the NCI-CBCTR. This work will be done in cooperation with the other resources of the NCI-CBCTR. 3: To maintain an adequate accrual of new cases that allows a replenishment of the used archival tissue. 4: To construct tissue microarray of normal breast tissue and further distribution to investigators whose applications have been recommended for approval by REP and by the NCI.CBCTR. 5: To maintain an adequate quality control in the FCCC-CBCTR. 6: To fully participate in the functioning of the coordinating Committee of the NCI Cooperative Breast Cancer Tissue Resource and to collaborate with the Research Evaluation Panel 7: To encourage the utilization of the NCI-CBCTR through an adequate marketing initiative.